Financial Instruments (Fair Value of Derivative Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Sep. 30, 2017
Derivative [Line Items]
Total Derivatives, Assets	$ 157.6	$ 227.8
Total Derivatives, Liabilities	151.6	131.9
Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	139.8	222.5
Total Derivatives, Liabilities	128.8	128.7
Designated as Hedging Instrument | Other Receivables | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	81.7	81.7
Designated as Hedging Instrument | Other Receivables | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	5.5	11.1
Designated as Hedging Instrument | Other Noncurrent Assets | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	9.1	27.1
Designated as Hedging Instrument | Other Noncurrent Assets | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	43.5	102.6
Designated as Hedging Instrument | Accrued Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	31.6	82.0
Designated as Hedging Instrument | Accrued Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	19.4	10.7
Designated as Hedging Instrument | Other Noncurrent Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	19.7	13.8
Designated as Hedging Instrument | Other Noncurrent Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	58.1	22.2
Not Designated as Hedging Instrument
Derivative [Line Items]
Total Derivatives, Assets	17.8	5.3
Total Derivatives, Liabilities	22.8	3.2
Not Designated as Hedging Instrument | Other Receivables | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	4.4	1.1
Not Designated as Hedging Instrument | Other Receivables | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	0.0	0.0
Not Designated as Hedging Instrument | Other Noncurrent Assets | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Assets	9.5	0.0
Not Designated as Hedging Instrument | Other Noncurrent Assets | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Assets	3.9	4.2
Not Designated as Hedging Instrument | Accrued Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	5.4	2.2
Not Designated as Hedging Instrument | Accrued Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	0.4	1.0
Not Designated as Hedging Instrument | Other Noncurrent Liabilities | Forward Exchange Contracts
Derivative [Line Items]
Total Derivatives, Liabilities	17.0	0.0
Not Designated as Hedging Instrument | Other Noncurrent Liabilities | Interest Rate Management Contract
Derivative [Line Items]
Total Derivatives, Liabilities	$ 0.0	$ 0.0